One in five distant galaxies could be hidden behind cosmic dust, scientists say, discovering two previously invisible systems 29 billion light-years away.
Experts discover two galaxies ‘strongly obscured by dust’ 29 billion light-years away
‘REBELS-12-2’ and ‘REBELS-29-2’ were found with the ALMA radio telescopes in Chile
Their existence suggests that a fifth of existing galaxies are still hidden by space dust.

Scientists have discovered two “previously invisible” galaxies located about 29 billion light years from Earth.

The two galaxies ‘strongly obscured by dust’, called REBELS-12-2 and REBELS-29-2, were found during observations with ALMA radio telescopes in the Atacama desert in Chile.

Both were previously undetectable to the optical lens of NASA’s Hubble Space Telescope, because they were hidden behind curtains of cosmic dust.

The astronomers who found them now estimate that up to 20 percent of the galaxies in the universe are similarly obscured, but humanity has yet to find them.

With the help of the giant ALMA (Atacama Large Milimeter Array) radio telescopes in the Atacama desert of Chile, the two invisible galaxies “suddenly appeared.” ALMA has five times better spatial resolution than the Hubble Space Telescope, as shown by this graph, which was key to the discovery.

But many of these ‘lost’ galaxies could one day be found by teams, including the upcoming James Webb Space Telescope.

The new study was conducted by researchers at the Niels Bohr Institute at the University of Copenhagen.

“We were looking at a sample of very distant galaxies, which we already knew existed from the Hubble Space Telescope,” said Pascal Oesch, associate professor at the Niels Bohr Institute.

Then we realized that two of them had a neighbor that we didn’t expect to be there at all.

“As these two neighboring galaxies are surrounded by dust, some of their light is blocked, making them invisible to Hubble.”

Hubble launched into low Earth orbit in 1990, while ALMA (Atacama Large Millimeter Array) ground-based radio telescopes began scientific observations in 2011.

The most advanced ALMA has five times better spatial resolution than the Hubble Space Telescope, which was key to the discovery.

ALMA combines the light from its 66 antennas to create a high-resolution image and spectra of the sky, and can capture radio waves emitted from the coldest and darkest depths in the universe.